1. Field of the Invention
This invention relates generally to a solid-state laser device. More particularly, the present invention relates to a semiconductor laser device which utilizes a semiconductor laser chip as a laser beam emitting element.
2. Description of the Prior Art
Various semiconductor laser devices have been heretofore proposed. One typical example of these is the one which is disclosed for example in U.S. Pat. No. 4,768,070 (Patented: Aug. 30, 1988; Applicant: Takizawa et al) or in Japanese Utility Model Application Laid-open No. 62-58066 (Laid-open: Apr. 10, 1987; Inventor: Toshiyiko Ishii).
Reference is now made to FIGS. 11 through 13 of the accompanying drawings to specifically describe the general arrangement of the typical semiconductor laser device disclosed in the above-noted U.S. patent or laid-open Japanese Utility Model application.
As shown in FIGS. 11 through 13, the typical prior art semiconductor laser device includes a discal base or stem 1 of a suitable diameter D and thickness T. The stem is provided with an upwardly directed mounting block 2 for mounting a semiconductor laser chip 3 via a semiconductor substrate (submount) 4. The discal stem is made of a metal such as carbon steel, and works dually as a support and as a heat sink.
The stem 1 is formed, near the mounting block 2, with an inclined recess 9a for arranging a laser emission monitoring photodiode 9. The underside of the stem is welded to a first lead 7a in electrical conduction therewith. Further, the stem is formed with a pair of lead inserting holes 1a, 1b to allow insertion of second and third leads 7b, 7c. The second and third leads are hermetically insulated from the stem by insulation sealant 8, such as glass, loaded into the respective lead inserting holes.
As shown in FIG. 12, the laser chip 3 is connected to the substrate 4 by a wire A, while the substrate 4 is connected to the second lead 7b by another wire B. Similarly, the third lead 7c is connected to the photodiode 9 by a further wire C.
The laser device further comprises a cap 5 having a glass window 6 and mounted to the stem 1 to encase the semiconductor laser chip 3 and its associated components. The cap is also made of a metal such as carbon steel, and hermetically attached to the stem by performing resistance welding.
In operation, when a predetermined current is passed, the semiconductor laser chip 3 generates a laser beam in the arrow direction (FIG. 11) by stimulated emission. Simultaneously, a small portion of the laser beam is emitted in the opposite direction and detected by the photodiode 9 for monitoring the laser beam emission.
According to the prior art described above, the mounting block 2 may be formed in two different methods.
Specifically, in a first method, the mounting block 2 is separately prepared, and subsequently fixed to the stem 1 by welding or brazing. However, the first method is disadvantageous in that the mounting block is likely to deviate positionally and/or angularly during the welding or brazing operation. Thus, after welding or brazing, it may be necessary to perform additional finish machining until the chip bonding surface of the mounting block 2 is located correctly relative to the center of the stem 1 and maintains exact perpendicularity relative to the stem surface, thus resulting in an unacceptable cost increase.
In a second method, the mounting block 2 is formed integrally with the stem 1 simultaneously at the time of preparing the stem by cold-forging. While improving the positional and angular accuracy of the mounting block, the second method is still disadvantageous in that cold-forging of the combined stem and mounting block requires a strong high-precision forging machine but nevertheless results in early damage of forging dies, consequently causing an unacceptable cost increase.
Further, regardless of the method of forming the mounting block 2, the mounting block 2 provides an additional weight which cannot be canceled in the prior art arrangement.